PriorityQueue

java.lang.Object
- PriorityQueue<E>

Type Parameters:

E -

All Implemented Interfaces:

QueueADT<PriorityQueueItem<E>>
```
public class PriorityQueue<E>
extends java.lang.Object
implements QueueADT<PriorityQueueItem<E>>
```
PriorityQueue implemented as a Binary Heap backed by an array. Implements QueueADT. Each entry in the PriorityQueue is of type PriorityQueueNode. First element is array[1]

Author:

CS367

Field Summary

Fields
Modifier and Type Field and Description

private PriorityQueueItem<E>[] array
The heap array.

private int currentSize

private int DEFAULT_CAPACITY

Fields
Modifier and Type	Field and Description
`private PriorityQueueItem<E>[]`	`array` The heap array.
`private int`	`currentSize`
`private int`	`DEFAULT_CAPACITY`

Constructor Summary

Constructors
Constructor and Description

PriorityQueue()
Construct an empty PriorityQueue.

PriorityQueue(PriorityQueue<E> pq)
Copy constructor

Constructors
Constructor and Description
`PriorityQueue()` Construct an empty PriorityQueue.
`PriorityQueue(PriorityQueue<E> pq)` Copy constructor

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`private void`	`buildHeap()` Heapify Establish heap order property from an arbitrary arrangement of items.
`void`	`clear()` Make this PriorityQueue empty.
`PriorityQueueItem<E>`	`dequeue()` Removes and returns the largest item in the priority queue.
`private void`	`doubleArray()` Internal method to expand array.
`void`	`enqueue(PriorityQueueItem<E> item)` Adds an item to this PriorityQueue.
`boolean`	`isEmpty()` Returns true iff the Queue is empty.
`java.util.Iterator<PriorityQueueItem<E>>`	`iterator()` Returns a PriorityQueueIterator.
`PriorityQueueItem<E>`	`peek()` Returns the largest item in the priority queue.
`private void`	`percolateDown(int hole)` Internal method to percolate down in the heap.
`int`	`size()` Returns the number of items in this PriorityQueue.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DEFAULT_CAPACITY
```
private final int DEFAULT_CAPACITY
```
    See Also:
    
    Constant Field Values
  - currentSize
```
private int currentSize
```
  - array
```
private PriorityQueueItem<E>[] array
```
    The heap array. First element is array[1]
- Constructor Detail
  - PriorityQueue
```
public PriorityQueue()
```
    Construct an empty PriorityQueue.
  - PriorityQueue
```
public PriorityQueue(PriorityQueue<E> pq)
```
    Copy constructor
    
    Parameters:
    
    pq - PriorityQueue object to be copied
- Method Detail
  - enqueue
```
public void enqueue(PriorityQueueItem<E> item)
```
    Adds an item to this PriorityQueue. If array is full, double the array size.
    
    Specified by:
    
    enqueue in interface QueueADT<PriorityQueueItem<E>>
    
    Parameters:
    
    item - object of type PriorityQueueItem.
  - size
```
public int size()
```
    Returns the number of items in this PriorityQueue.
    
    Specified by:
    
    size in interface QueueADT<PriorityQueueItem<E>>
    
    Returns:
    
    the number of items in this PriorityQueue.
  - iterator
```
public java.util.Iterator<PriorityQueueItem<E>> iterator()
```
    Returns a PriorityQueueIterator. The iterator should return the PriorityQueueItems in order of decreasing priority.
    
    Returns:
    
    iterator over the elements in this PriorityQueue
  - peek
```
public PriorityQueueItem<E> peek()
```
    Returns the largest item in the priority queue.
    
    Specified by:
    
    peek in interface QueueADT<PriorityQueueItem<E>>
    
    Returns:
    
    the largest item.
    
    Throws:
    
    java.util.NoSuchElementException - if empty.
  - dequeue
```
public PriorityQueueItem<E> dequeue()
```
    Removes and returns the largest item in the priority queue. Switch last element with removed element, and percolate down.
    
    Specified by:
    
    dequeue in interface QueueADT<PriorityQueueItem<E>>
    
    Returns:
    
    the largest item.
    
    Throws:
    
    java.util.NoSuchElementException - if empty.
  - buildHeap
```
private void buildHeap()
```
    Heapify Establish heap order property from an arbitrary arrangement of items. ie, initial array that does not satisfy heap property. Runs in linear time.
  - clear
```
public void clear()
```
    Make this PriorityQueue empty.
    
    Specified by:
    
    clear in interface QueueADT<PriorityQueueItem<E>>
  - percolateDown
```
private void percolateDown(int hole)
```
    Internal method to percolate down in the heap. Wiki}
    
    Parameters:
    
    hole - the index at which the percolate begins.
  - doubleArray
```
private void doubleArray()
```
    Internal method to expand array.
  - isEmpty
```
public boolean isEmpty()
```
    Description copied from interface: QueueADT
    
    Returns true iff the Queue is empty.
    
    Specified by:
    
    isEmpty in interface QueueADT<PriorityQueueItem<E>>
    
    Returns:
    
    true if queue is empty; otherwise false.

Class PriorityQueue<E>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_CAPACITY

currentSize

array

Constructor Detail

PriorityQueue

PriorityQueue

Method Detail

enqueue

size

iterator

peek

dequeue

buildHeap

clear

percolateDown

doubleArray

isEmpty